It is the latest development in a nationwide effort to place every aspect of hip-hop culture under state surveillance.

Miami officials say the binder was given to them by the New York police department during a three-day "hip-hop training session" in May that was also attended by officers from Atlanta and Los Angeles.

"Everyone that went got a binder with information on rappers that have been arrested, outlining charges," says Miami police sergeant Rafael Tapanes.

"They were trained what to look for in the lyrics, what to look for when they go to hip-hop concerts, what radio stations and TV stations to monitor to keep abreast of any rift between these rappers."

Miami police say they are just doing their job, monitoring a section of the music industry that has lost some of its most prominent talent, including Tupac Shakur, the Notorious BIG and Jam Master Jay, to violence.

"We have to keep an eye on these rivalries," the Miami Beach assistant police chief, Charles Press, told the Miami Herald. "What would law enforcement be if we closed our eyes? Our job is to know as much about things that could hurt innocent people."

Racial stereotyping
But rappers and civil rights advocates say it is an unnecessary intrusion on their civil liberties that smacks of racial profiling. "This kind of conduct shows insensitivity to constitutional limitations," says Bruce Rogow, a lawyer who represented 2 Live Crew in their successful defence against obscenity charges in the early 1990s. "It also implicates racial stereotyping."

The rap world has all the terminology of a modern state, it was only a matter of time before it got a dedicated police unit.

What has become known as the hip-hop "nation" is governed by a hip-hop "generation", where conflicts are resolved and agendas mapped out at hip-hop "summits", during which the hip-hop "community" decide how to protect and promote hip-hop "culture".

Rap is an adversarial genre in which artists do battle through their lyrics. In the past few years, there has been a concerted attempt to channel the creative energy - and billions of dollars - that have emerged into political activism, social responsibility and lobbying. This has been done most notably by rap impresario Russell Simmons through his Hip-Hop Summit Action Network.

Meanwhile, rappers have tried to improve their image. After running the marathon, P Diddy (who was acquitted of gun possession and bribing a witness in 2001 after a shoot-out in a New York nightclub) donated $2m (now £1.1m) to the children of New York city.

On her single Wake Up, Missy Elliott sings: "If you don't got a gun, it's all right/ If you're makin' legal money, it's all right."

The hip-hop label Murder Inc, which is under investigation by nearly a dozen law enforcement agencies for (among other things) its relationships with drug traffickers, has said it will drop the word "murder" from its title.

None the less, violence, all too often explicit in the lyrics, can spill out into real life with deadly consequences.

Last week, Chauncey Hawkins (otherwise known as Rapper Loon) was charged with assault with a deadly weapon after attacking a guard in Los Angeles.

Six months ago, Gerard Fields, 26, a rapper with what was Murder Inc, was shot dead. And, in recent times, there have been several attempts on the life of 50 Cent.

The intensity has abated since the east coast/west coast rivalry of the mid-1990s, which took the lives of two of rap's most promising stars: the Notorious BIG and Tupac Shakur.

Monitoring the 'crews'
But 18 months ago, Jam Master Jay, the DJ for Run-DMC, was shot in the head as he sat on a sofa in the lounge of a recording studio. Jay's murder sparked the NYPD to establish a special section within its gang intelligence unit. According to the New York Times, a team of six detectives monitor sales and keep track of the movements of different "crews" to make sure that rivals do not get in each other's way.

Miami police started collecting data after 250,000 hip-hop fans came to South Beach for a four-day party and there were 211 arrests, mostly for disorderly conduct and excessive drinking.

While no rap stars were arrested, the police felt their ignorance left them vulnerable. "Nobody on the beach had a handle on who the players were," said Mr Press.

"We didn't know anything, we didn't know who were the big record labels, who were the kingpins; we didn't know why there were rivalries with Ja Rule and Eminem."